The two most urgent needs with respect to the development of improvements in internal combustion engines during the past years have been those related to the lowering of air pollution and those relating to the need for increased fuel economy. The present invention relates to both those objectives in a manner which will be described as follows:
The Wankel engine has been of interest to the automobile producers because of its inherent simplicity, relatively light weight and relatively small size with regard to a piston engine or comparable power output. While the Wankel engine is of interest to the automotive producers because of its small size, its inherent wastefulness at speeds other than full throttle speeds has precluded the attainment of reasonable mileage values.
The Wankel engine, because of its smaller size does, however, allow the installation of anti-pollution devices under the hood in addition to the engine which could not be done with a piston engine of comparable power output since these already occupied almost the total volume under the hood of the standard automobile.
Atmospheric pollution, as it is related to the internal combustion engine, is caused principally by the emission through the exhaust of unburned hydrocarbons, carbon monoxide, and a mixture of nitrogen oxides. A number of approaches have been tried with varying degrees of success to lower these emissions.
The two goals of high efficiency which would result in good fuel economy and of low emission of pollutants are not easily obtainable in the same operating invention. An engine which operates at high efficiency will do so principally by the use of high compression ratio and operate at high temperatures but will usually result in an engine which emits a relatively large amount of nitrogen oxide, carbon monoxide and unburned hydrocarbons.
The necessity for controlling pollutants has caused drastic changes in the design of the internal combustion engine as presently manufactured in the United States. The Wankel engine originally proposed provides an alternative on the basis of its smaller size, lighter weight and simplicity in mechanical design. The initial enthusiasm for the Wankel engine in the recent past was based upon its smaller size which designers felt would enable them to add anti-pollution devices under the hood in the same space as is now used by the conventional piston engine. However, several deficiencies of the Wankel engine soon became apparent. The invention itself in operation is comparatively poor in fuel economy and passes large amounts of hydrocarbons into the atmosphere, necessitating a larger afterburner catalytic converter or other anti-pollution devices to be used. It was also found that the apex seals in the Wankel engine wear rapidly and have to be replaced after a relatively short operating life. One of the particularly unacceptable shortcomings of the Wankel engine is high fuel consumption at low speeds or idling.
The present invention seeks to alleviate both of the deficiencies by the invention of controlling the amount of air when the engine is operating at less than full throttle open, then lowering fuel consumption by allowing the idling engine to operate at a leaner mixture of fuel-air and lengthening the seal life by lowering the temperature of operation.